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Twenty-four seats stand between Democrats and their control of the U.S. House of Representatives now held by Republicans, with Southern California seen as crucial to the Democrats’ effort to retake the House in the 2018 midterm elections.

Efforts by Democrats to flip the seats are heating up in the nine districts:

CA-10: Jeff Denham (R-Turlock)

CA-21: David Valadao (R-Hanford)

CA-22: Devin Nunes (R-Visalia)

CA-25: Steve Knight (R-Palmdale)

CA-39: Ed Royce (R-Fullerton)

CA-45: Mimi Walters (R-Irvine)

CA-48: Dana Rohrabacher (R-Costa Mesa)

CA-49: Darrell Issa (R-Vista)

CA-50: Duncan Hunter (R-Temecula)

Perhaps nowhere is the political activity as intense as in Issa's district.

At a recent rally outside the Republican congressman office in the northern San Diego County city of Vista, opponents of the congressman sang a protest song riffing off the "Gilligan's Island" tune and shouted slogans.

Ever since the election of President Donald Trump last November, the gatherings have become a regular Tuesday event. Many people, including Carlsbad resident Mary Schrader, show up each week.

Schrader said before Trump was elected, she had never been to a political rally. In fact, she said she was a registered Republican and voted for John Kasich in last year’s presidential primary. Then she switched parties and voted for Hillary Clinton in November.

"When Trump got elected, I spent the first day crying, huddled in a mass on my bed, and the following day said, 'OK, now it’s time,'" she said. That's time to fight for issues she said she believes in, like human rights, preserving the Affordable Care Act and getting Issa out of office.

"I do feel that Issa does not represent us … And that's a problem, that’s a huge problem," she said.

Issa, an early supporter of Donald Trump and frequent critic of Barack Obama, has largely side-stepped the weekly protests, although he has made previous appearances before the Vista crowds.

His office did not respond to requests for comment for this story. But at a February rally he told a large crowd he hoped to find a way "to bridge these two groups," referring to his supporters and those protesting against him. KPBS reported he spent an hour answering the crowd's questions, which were largely focused on immigration and healthcare concerns.

Of the 300 or so people at the recent rally, the vast majority opposed Issa. But a handful supported the congressman and President Trump.

Oceanside resident Sean Colgan, who says he's known as the Trump Motorcycle Guy on Facebook, showed up at the recent rally with signs attached to his motorcycle reflecting his conservative values. Colgan said he's an Issa supporter.

"He’s strong for the Second Amendment, he’s strong on the reality that healthcare is not a right that should be paid for by the government, not necessarily," Colgan said.

He points out one challenge for the Democrats will be motivating voters who aren’t regular voters.

Midterm elections in California historically have low participation rates, particularly among newer voters and people of color. That results in more clout for older, white homeowners who tend to vote at higher rates.

But voter registration in Issa's 49th congressional district, which includes parts of southern Orange County, has shifted over time. A decade ago, registered Republicans made up nearly half of the district's voters, but since then that’s dropped by about 10 percentage points.

Democratic operatives are trying to take advantage of those changes.

Drew Godinich works for the Democratic Congressional Campaign Committee as its western regional press secretary. He’s part of a team of staffers who relocated from Washington, D.C., to an office in Irvine, focusing their efforts on flipping the GOP seats in California.

"I think one of the big reasons that the DCCC saw fit to establish an office out here was, you know, we realized like you can’t from D.C., you’re not getting the full picture of what’s happening on the ground," he said. "It's really important for us to get a sense of that and to try to translate that into our messaging."

Godinich said part of the party's strategy is to understand what’s motivating voters here, and apply that knowledge in other congressional districts. The DCCC staffers are also busy organizing and collecting contact information, so that they can mobilize voters come the election next year.

Longtime Democratic political strategist Darry Sragow says it's bold of the DCCC to invest resources in Southern California, but it remains to be seen whether the new Irvine office will help turn out voters.

"Is President Trump putting politics on the front burner for many Americans? Sure... there's no question about it. Is it going to motivate them to turn out and vote? Well, that all depends. It depends on what their choices are ... we don't know," he said.

Rob Stutzman, a political consultant for GOP candidates who has worked on campaigns for Arnold Schwarzenegger and Meg Whitman, said Republicans are likely in for a bumpy midterm but he doesn't expect it to be disastrous for the GOP.

"We're still a year away from the general election," Stutzman said. "There's been a lot of enthusiasm on the left with the advent of the Trump administration, but I think you have to allow for some of that to wane."

The local protesters at Issa's Vista office said they are prepared to rally through the November 2018 general election. The Democrats from D.C. they say they’ll keep attending, too, and working to deliver votes for the election.

Next year's primary is scheduled for June 5 and the general is set for Nov. 6.